The present invention generally relates to an automobile internal combustion engine and, more particularly, to a device for interrupting the supply of air-fuel mixture to some of the engine cylinders during a particular engine operating condition.
The U.S. Pat. No. 3,578,116, patented on May 11, 1971, discloses a conventional device for interrupting the supply of air-fuel mixture to some of the engine cylinders or combustion chambers during idling or deceleration to improve the combustion conditions so that any possible waste of fuel and any possible emission of a relatively large amount of noxious unburned components of the exhaust gases to the atmosphere can be minimized or substantially eliminated. This conventional device is applicable to a multi-cylinder internal combustion engine of a type having at least two engine cylinders or combustion chambers communicated with a source of air-fuel mixture, that is, a carburetor, through an intake manifold of a type including a common duct, having one end communicated with the air-fuel mixture source, and first and second branch ducts ramified from the other end of the common duct and leading to the respective engine cylinders.
The conventional device for selective combustion in the multi-cylinder engine such as disclosed in the above mentioned U.S. patent comprises a shutter or butterfly valve operatively positioned in the first branch duct for selectively closing and opening the first branch duct and normally biased to close the first branch duct by a biasing spring element, said shutter valve being pivoted in a direction against the biasing spring element to open the first branch duct in response to increase of the negative pressure which would take place inside a portion of the first branch duct upstream of the shutter valve with respect to the direction of flow of the air-fuel mixture towards the corresponding engine cylinder during idling or deceleration of the automobile engine. During the closure of the first branch duct, not only is the air-fuel mixture, which would have been introduced into the engine cylinder communicated with the first branch duct, caused to flow into the second branch duct and then towards the other engine cylinder, but also fresh air is introduced into the first branch duct at a position downstream of the shutter valve in the closed position.
In order for the shutter valve to operate in the manner described above, the conventional device further comprises an actuator, comprised of a cylindrical casing and a piston member axially slidably housed within the cylindrical casing and operatively coupled through an operating rod to the shutter valve, a switching valve assembly which is either a cylinder-and-piston arrangement or an electromagnetically operated valve device and which is operable to selectively establish and interrupt the communication between that portion of the first branch duct upstream of the shutter valve and a working chamber within the cylindrical casing, and a normally closed shut-off valve assembly including a valve member so designed as to be engageable with an engagement fast with the operating rod during the movement of the operating rod in such a direction as to bring the shutter valve into the closed position so that the fresh air can be introduced into the first branch duct at a position downstream of the shutter valve.
In this construction, the switching valve assembly is held in one position to establish the communication between that portion of the first branch duct upstream of the shutter valve and the working chamber inside the cylindrical casing when a piston element is displaced against a biasing element by the effect of a negative pressure drawn thereto from that portion of the first branch duct, and the switching valve assembly is movable to another position to interrupt the above described communication when the negative pressure so drawn thereto from that portion of the first branch duct is of a value lower than the biasing force of the biasing element. While the working chamber inside the cylindrical casing of the actuator is communicated with the atmosphere through the switching valve assembly during the incommunication between that portion of the first branch duct and the working chamber, the negative pressure introduced into the working chamber during the communication therebetween draws the piston member of the actuator and, hence, the operating rod in such a direction so as to bring the shutter valve into the closed position.
The conventional device of the above described construction is complicated in structure, since the combination of the actuator with the switching valve assembly and the shut-off valve assembly are utilized separately. Moreover, the conventional device employs a relatively large number of separate movable parts, such as the piston member in the actuator, the piston element in the switching valve assembly and the valve member in the shut-off valve assembly. Accordingly, the conventional device appears to be less reliable in operation in addition to the requirement of the increased manufacturing cost.